Download Preventing Transaction Logs From Filling Up

Database Maintenance
NewsBrowse utilizes the SQL full recovery model and a maintenance plan is
essential to keeping the database in working order. Not only does the database need to be
backed up but the accompanying transaction log needs to be backed up as well. Failure to
back up the transaction log can cause the database to become inoperable due to the file
growing too large. This document will cover the steps necessary to recover in the event
that the transaction log has grown too large, manual truncation of the transaction log
before it becomes a problem and how to schedule a maintenance plan.
The transaction log is responsible for keeping track of all the edits to data until it
reaches what is known as a checkpoint. Once the checkpoint is reached, the data should
be permanently committed to the database. What we may be experiencing is that this
checkpoint is reached, data is not committed to the database, and the transaction log
continues to grow. If the transaction log reaches the capacity of growth it can render the
database inoperable. In the event that the database has been rendered inoperable a manual
truncation of the transaction log will need to be performed. It is a good practice to
monitor the growth of the transaction log daily, frequently backup the transaction log and
shrink the file to release disk resources to the operating system. The following will be
described below:
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The database is rendered inoperable due to the transaction log becoming too
large.
How to determine the size of the transaction log.
Manually controlling transaction log growth.
Setting up a database maintenance plan.
The database is rendered inoperable due to the transaction log
becoming too large
If this is the current scenario it is highly likely that the transaction log has never
been backed up, a database maintenance plan has not been enabled on the system or the
SQL Server agent is not running to implement you maintenance plan. The following steps
should resolve the problem.
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Open SQL Query Analyzer
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Make sure the database in question is selected in the top tool bar. (For this
example the ThomsonAM database will be used. The code will be the same for
Thomson_Ingest and Thomson_RulesWizard )
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First try to backup the transaction log with out truncating it by running the
following command:
 BACKUP LOG ThomsonAM TO Disk = ‘filePath\fileName.trn'
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Where filePath and fileName is user specified, (e.g. D:\Emergency
Backups\ThomsonAM_tran_12052003.trn) if the file does not already
exist, you will need to create it. If the transaction log is full it is likely that
this command will fail but it is important to try it to maintain database
integrity.
Regardless the previous command passes or fails execute the following command
to clear the transaction log
 BACKUP LOG ThomsonAM WITH TRUNCATE_ONLY
To free unused resources to the operating system execute the following command
 DBCC SHRINKFILE(ThomsonAM_log, 2)
How to determine the size of the transaction log
When SQL is installed the space that it is allotted on the operating system is
divided into two parts, 50% is given to store transaction logs 50% is reserved for data. To
identify the amount of space the transaction logs is taking up open, SQL Query Analyzer
and execute the following command.
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DBCC sqlperf(logspace)
This command will return the amount of space each databases transaction log is taking up
and the percentage of space the transaction log is using. The column that lists the percent
of space the transaction log is taking up is misleading. NewsBrowse databases set the
transaction log growth limit to 500MB. If one of the databases transaction logs is lager
than 350MB then follow the steps in the Manually controlling transaction log growth
section of this document.
Manually controlling transaction log growth
The transaction log is approaching its size limit. First back up the database and
the transaction log to keep a record of its current state. The flush and shrink the
transaction log file to reduce its size. To do this open SQL Enterprise Manager and
manually backup the database and transaction log of the database in question. The steps
to do this are as follows:
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From the Enterprise Manager right mouse click the database in question; select
All Tasks\ Backup Database…
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Make sure that the Database Complete radio button is selected
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In the Destination section under Backup to:, check the file path and make sure
the file has a (.bak) extension. If it does not have a (.bak) extension or the path is
not where you would like the backup file to reside, click the Remove button to
remove the file and the associated path. Click the Add… button browse to the
directory to where you would like to store the file. Make sure you give it a file
name with the (.bak) file extension. (For example: D:\DB\ThomsonAM.bak)
Click the OK button and verify that the path entered is listed in the Backup to:
list.
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In the Overwrite section make sure that overwrite existing media radio button is
selected.
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Click the OK button to backup the database.
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To backup the transaction log the steps are very similar. Open the Enterprise
Manager right mouse click the database in question, select All Tasks\ Backup
Database…
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Make sure that the Transaction log radio button is selected.
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In the Destination section under Backup to:, check the file path and make sure
the file has a (.trn) extension. If it does not have a (.trn) extension or the path is
not where you would like the backup file to reside, click the Remove button to
remove the file and the associated path. Click the Add… button browse to the
directory to where you would like to store the file. Make sure you give it a file
name with the (.trn) file extension. (For example: D:\DB\ThomsonAM.trn)
Click the OK button and verify that the path entered is listed in the Backup to:
list.
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In the Overwrite section make sure that overwrite existing media radio button is
selected.
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Click the OK button to backup the Transaction log.
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Open SQL Query Analyzer
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Make sure the database in question is selected in the top tool bar.
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Execute the following code
o BACKUP LOG ThomsonAM WITH TRUNCATE_ONLY
o DBCC SHRINKFILE(ThomsonAM_log, 2)
Setting up a database maintenance plan
The best way to control the growth of transaction logs is to simply back them up.
Once a day at the very least. SQL 2000 makes it very easy to set up a database
maintenance schedule. Before you begin implementing a database maintenance plan
using the SQL 2000 Database Maintenance Planner wizard make sure that the
SQLSERVERAGENT service is started and it properties are set to auto start for a local
system account. If the SQLSERVERAGENT is not running, the database maintenance
plan will not run. The following steps will describe how to launch and configure the SQL
2000 Database Maintenance Planner:
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Open SQL 2000 Enterprise Manager
Expand a Microsoft SQL Servers, expand the SQL Server Group and select the
SQL server.
On the Tools menu, click Database Maintenance Planner…
After the wizard launches click the Next> button
Select These databases radio button and select the Thomson_Ingest,
Thomson_RulesWizard and ThomsonAM databases.
Click the Next> button to navigate to the Update Data Optimization
Information page.
Select the Update statistics used by query optimizer. Sample Check box and
set it to 10% of the database.
Check the schedule to verify that the time scheduled will not conflict with peak
usage of the system. If a schedule, time change is needed click the Change…
button to modify the time. This option can be run daily but once a week is good.
Click the Next> button to navigate to the Database Integrity Check page.
Select the Check database integrity check box
Select the Include indexes radio button
Select the Attempt to repair any minor problems check box
Select the Perform these checks before doing backups check box.
Check the schedule to verify that the time scheduled will not conflict with peak
usage of the system. If a schedule, time change is needed click the Change…
button to modify the time. This option can be run daily but once a week is good.
Click the Next> button to navigate to the Specify the Database Backup plan
page
Select Back up the database as part of the maintenance plan check box
Select Verify the integrity of the backup when complete check box
Select the Disk radio button
Change the schedule from once a week to daily by clicking the Change… button
Select the Daily radio button and set the interval to Every 1 day(s)
Select the Occurs once at radio button if the default time of 2:00:00 AM is not
good; change it to a more suitable time.
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Make sure that the Start Date is today’s date and that the No end date radio
button is selected.
Click the OK button and verify the schedule.
Click the Next> button to navigate to the Specify Backup Disk Directory page.
Select the Use the default backup directory radio button. Unless the site has a
specific folder for database backup files. Then select the Use this directory radio
button and enter in the specified path. (Note: SQL can only see local drives and
cannot see shared directories or disks that are not native to the machine.)
Select the Create a subdirectory for each database check box
Select the Remove files older than check box and set the value to 1 week(s)
The backup extension should be set to BAK
Click the Next> button to navigate to the Specify Transaction Log Back up
Plan page.
Select Back up the transaction log as part of the maintenance plan check box
Select Verify the integrity of the backup when complete check box
Select the Disk radio button
Click the Change… button to set the transaction log schedule
Select the Daily radio button and set the interval to Every 1 day(s)
Select the Occurs every radio button and set the interval to every 6 hours
Make sure that the Start Date is today’s date and that the No end date radio
button is selected.
Click the OK button and verify the schedule.
Click the Next> button to navigate to the Specify Transaction Log Backup Disk
Directory page
Select the Use the default backup directory radio button. Unless the site has a
specific folder for database backup files. Then select the Use this directory radio
button and enter in the specified path. (Note: SQL can only see local drives and
cannot see shared directories or disks that are not native to the machine.)
Select the Create a subdirectory for each database check box
Select the Remove files older than check box and set the value to 1 week(s)
The backup extension should be set to TRN
Click the Next> button to navigate to the Reports to Generate page
Click the Next> button to navigate to the Maintenance Plan History page
Click the Next> button to navigate to the Completing the Database
Maintenance Plan Wizard page
Enter NewsBrowse for the name of the schedule.
Click the Finish button. (Note: If an error occurs, it is most likely that your
SQLSERVERAGENT was not started. Start the service and start over.)
If the SQLSERVERAGENT is ever stopped, so is your maintenance plan. Make
sure that the service is set to auto start in case of a reboot.